1. Field of the Invention
The present invention relates to a semiconductor integrated circuit apparatus and a control method thereof, in particular, a semiconductor integrated circuit apparatus having a circuit for saving and recovering data representing internal state and a control method thereof.
2. Description of the Related Art
In recent years, attention is being given to a semiconductor integrated circuit having a low power consumption mode such as a standby-function and a resume function. Generally, in the semiconductor integrated circuit, except for a nonvolatile memory, an internal state is erased when a power supply is stopped. Thus, when the power supply is restarted, to restart the circuit operation from the state immediately before the power supply to the circuit was stopped, the internal state needs to be stored.
For example, Japanese Laid-Open Patent Application JP-A-Heisei 06-52070 discloses an integrated circuit for saving and holding internal state data held in registers in an external memory at the time of stopping of the power supply. This integrated circuit has a plurality of registers, a data saving portion and a data recovery portion. The plurality of registers is connected to form scan chains. The data saving portion responds to an external signal, allows the plurality of registers to form the scan chains in a data saving mode and reads out the data held in each register through the formed scan chains. At this time, the data saving portion serially/parallelly converts the internal state data into data with a predetermined bit width and stores the converted data in a data protection memory through a data input/output portion. In response to the external signal, the data saving portion allows the plurality of registers to form the scan chains and recovers the saved data to the original register through the formed scan chains in a data recovery mode. At this time, the data saving portion reads out the internal state data from the data protection memory, receives it from the data input/output means and converts the data with the predetermined bit width into serial internal state data to be recovered through the scan chains.
As described above, to store the internal state of the semiconductor integrated circuit apparatus, a battery backed-up memory is required.